A control valve is typically used to control the flow of a fluid under pressure. The valve can be “opened” to allow or increase fluid flow, and can also be “closed” to prevent or reduce the flow of fluid. As a result, by controlling the opening and closing of the valve, flow rate of the fluid can be changed. In some applications the fluid may be under high pressure, and the actuation of the valve requires relatively high actuation forces to overcome the pressure and open or close the valve. In some applications, precisely controlling the actuation of the valve, for example, opening or closing the valve by a repeatable and small amount or with minimal backlash, is desirable. Also, it may be desirable in some applications to be able to quickly and accurately adjust the opening or closing of a valve.
An example of a control valve is a motor driven needle valve. Although motor driven needle valves typically consume little power and provide high actuation forces, they may be slow to respond and exhibit behavior that reduces sensitivity and resolution, such as backlash. Another example of a control valve is a solenoid driven valve. Although these valves are fast and provide good resolution, these valves typically consume a large amount of power and provide limited actuation forces.